A casual boating trip offshore New Smyrna Beach turned into a life and death struggle for four boaters on Thanksgiving Day. They left the boat ramp around 5 am and were enjoying a morning catching many fish about 12 miles offshore, but suddenly the boat started to take on water and capsized around 10 am. The four spent the rest of the day and night clinging to the side of the boat before being rescued around 10 am on Friday about 25 miles offshore.

The 12Z surface map showed a rather tight gradient across the area producing a moderately strong offshore wind flow. The morning forecast captured the dangers well and called for west/southwest winds at 15 to 20 knots with a Small Craft Exercise Caution for Winds headline near shore. A Small Craft Advisory for Winds was in effect beyond 20 nm. The boaters may have been fooled by flat seas at the boat ramp. Also they weren't going to be going very far offshore. However, the winds probably exceeded the 15-20 knots in the forecast as buoys 41009 and 41012 reported 20-25 knots most of the day. Seas were around 4 feet at 41009 but were 5-6 feet at 41012. Very short period waves (4-5 second period) produced choppy conditions. One boater's comment that "a swell hit us" is inaccurate as the wave was not a swell. It was a short period wind wave, probably 4+ feet with a 4 second period, which is very steep.

The forecast was handled well by having headlines in the forecast. Seas at 2 to 3 feet with a 15-20 knot wind may have been confusing, but with a warm advection pattern and offshore winds, there was low level stability (warmer air flowing over cooler water) and limited fetch. Seas may have been more like 1-2 feet near shore and 3-4 feet at 20 nm. Normally that is not something that boaters would get worried about though. Of course, based on wave theory, 1 in a 100 waves would be 1.67 times higher or approximately 5-6 feet. This may have been the "swell" that one of the boaters referred to. These higher waves can occur quite frequently too, once every 5-10 minutes. After a while, water accumulating in the bottom of the boat can make it unstable.

One issue that this case raises is the need to know about wave steepness as the short period of the waves was the main causative factor. One of the goals for the Coastal Waters Forecast is to incorporate a wave steepness value. Another issue is that the boaters were probably looking at the 10 pm forecast from the night before. That forecast correctly bumped up winds to15-20 knots for the first period of the forecast and added a SCEC statement (good!), but the Thanksgiving Day forecast still had 10-15 knots. Sometimes when the forecaster updates period one, the second period will need some adjustment also (a lot of boating decisions are made the night before).

In conclusion, this was a rather rare case where seas were substantially lower than normal exercise caution criteria, but the west winds were strong enough to generate choppy short period waves which produced dangerous conditions for small craft. Also, this is another example of how vital the "exercise caution" statement is in Florida since there are so many "weekend warriors" operating very small boats.

.SYNOPSIS...DEEP LOW PRESSURE OVER THE GREAT LAKES...WITH RIDGE AXIS SUPPRESSED TO OUR SOUTH...WILL PRODUCE GUSTY OFFSHORE WINDS
TODAY. A WEAK COLD FRONT WILL DISSIPATE AS IT PUSHES DOWN THE FLORIDA PENINSULA FRIDAY. HIGH PRESSURE BUILDING ACROSS THE
SOUTHEAST AND INTO THE ATLANTIC WILL RESULT IN WINDS SHIFTING TO THE NORTHEAST SATURDAY AND GRADUALLY VEERING TO THE SOUTHEAST BY
MONDAY.